Poly(alkylene oxide) polymers, also referred to as polyether polyols, may be obtained by processes comprising contacting initiator with alkylene oxide in the presence of a catalyst. The alkylene oxide can in principle be any alkylene oxide such as ethylene oxide, propylene oxide and butylene oxide. However, the alkylene oxides most frequently used commercially are propylene oxide and ethylene oxide. Conventionally, basic catalysts like potassium hydroxide are used in the preparation of polyoxyalkylene polyether products. However, double metal cyanide (DMC) catalysts have been found to be especially advantageous in the continuous preparation of alkylene oxide reaction products.
DMC catalysts generally require an induction period before the catalyst becomes active. In this induction period, the catalyst is mixed with initiator while traces of water and air are removed. The catalyst is considered to be activated if there is a noticeable pressure drop following initial introduction of alkylene oxide. Following activation, polymerization proceeds rapidly when additional alkylene oxide is added. Preactivated catalyst/initiator mixtures may be stored for later use provided that care is taken to exclude moisture, oxygen, etc. Low molecular weight initiators tend to have lengthy induction periods, and in some cases, with low molecular weight initiators such as water, ethylene glycol and propylene glycol, the DMC catalyst may not become activated, or is temporarily activated followed by deactivation.
Once activated, low molecular weight initiator tends to be less efficient with DMC catalysts. Propylene glycol and water, for example, often oxyalkylate very sluggishly, and sometimes deactivate the DMC catalyst. For this reason, higher molecular weight initiators, for example those having molecular weights in the range of from 100 to 5000, are generally used. Such initiator may be prepared by traditional base catalysis. However, the basic catalyst must be scrupulously removed from these starters, as even traces of strong bases deactivate DMC catalysts.
It would be useful to prepare an alkoxylated initiator in such a way that it can be used as such in a DMC catalyzed process.